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• • • Astra 2017
Robotic capture using DEOS
7/14/2017 2
Introduction: Present day challenges
e.Deorbit clamping the target
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• Robustness against measurement noise and outliers for smooth control in presence of orbital
disturbances
• Allowing Visual servoing during times of occlusion and bad lighting conditions
• Parameter Estimation (geometry/inertial)
• Long-term Prediction of relative trajectory parameters
• Framework for Multiple Sensor Fusion by using measurements from several sensors
Introduction : Need for estimator
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Pose estimates of Target in camera frame
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Introduction: Need for estimator
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Simulated scenario of the grasping problem at DLR's
OOS-simulator Body diagrams of servicer and tumbling
target
7/14/2017 6
• Quaternion kinematics
• Newton-Euler equations
• Hill-Clohessy-Wiltshire equations
Introduction : Modeling
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Introduction : Visual servoing
Visual servoing on the On-Orbit Servicer
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• Larger Sampling intervals
• Higher presence of Outliers (not Gaussian)
• Varying noise characteristics due to changing lighting conditions and occlusion
• Due to delay in image-processing, the recent available measurement is a snapshot of a past state
Introduction : Vision System Characteristics
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• A Bayesian approach is used
• Variational Bayesian inferencing is used to approximate posterior distributions
• An Inv-Gamma distribution is assumed on diagonal elements
Estimation (new approaches) : Adaptive EKF
• Algorithm-1 is an iterative scheme which adapts in 3-4 steps
• Minimize Kullback-Leibler (KL) divergence to obtain iterative formulation
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Estimation (new approaches) : Outlier Rejection
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Estimation (new approaches) : Out-of-Sequence Measurements
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Estimation (new approaches) : Visual Servoing
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Estimated and Measured pose
Results : EKF
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Velocities and Inertia
Results : EKF
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Grasping point’s pose (estimated)
Results : EKF
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Pose of target center of mass w.r.t servicer’s center of mass
Results : EKF
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Results : EKF
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Results : EKF
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Results : EKF (OOSM)
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Results : EKF
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• Smooth Visual Servoing is possible due to filtered estimates of motion parameters
• Vision sensor issues were handled with computationally efficient algorithms for Parameter Estimation
• Model developed to incorporate Robot kinematics for PBVS
• With OOSM and Parallel updates, multiple sensor fusion can be used to improve estimates
• Subsequent research naturally lends towards evaluation of the proposed estimator with DLR-OOS data.
Conclusion
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